Hi,
I am considering now the timings during a BLE connection, especially for long range. For that I came across the range delay given in the latest BT Link Layer Specification. From the Air Interface protocol 21 January 2019, BLUETOOTH CORE SPECIFICATION Version 5.1 | Vol 6, Part B page 2743 (Bluetooth SIG Proprietary):
4.2.3 Range delay
Where two devices are more than a few meters apart the time taken for a signal to propagate between them will be significant compared with the Active Clock Accuracy defined in Section 4.2.1. When a device is listening for a packet that might be up to D meters away, it should listen for an extra 2D * 4 ns after the nominal latest time (e.g. T_IFS + 2 μs) that the packet would have been transmitted.
(1/c ~= 3.3 * refractive index ns/m, so 4 ns gives a conservative allowance.)
So the question is: Starting from BT 5.0, are the radios having a mechanism for estimating D and/or adjusting the duration of how much longer they should listen? If yes, how and when is that done?
For reference, here’s the delay in µs calculated according to the given equation for some D meters:
| Distance (m) | Delay (us) |
| 1 | 0,008 |
| 10 | 0,08 |
| 50 | 0,4 |
| 100 | 0,8 |
| 500 | 4 |
| 1000 | 8 |
One can see for long range connections, the delay starts getting in the us range!
Thanks.
